Buggy code:
public class FileUtils { public FileUtils ( ) { } public static final long ONE_KB = 1024 ; public static final BigInteger ONE_KB_BI = BigInteger . valueOf ( FileUtils . ONE_KB ) ; public static final long ONE_MB = ( FileUtils . ONE_KB ) * ( FileUtils . ONE_KB ) ; public static final BigInteger ONE_MB_BI = FileUtils . ONE_KB_BI . multiply ( FileUtils . ONE_KB_BI ) ; private static final long FILE_COPY_BUFFER_SIZE = ( FileUtils . ONE_MB ) * 30 ; public static final long ONE_GB = ( FileUtils . ONE_KB ) * ( FileUtils . ONE_MB ) ; public static final BigInteger ONE_GB_BI = FileUtils . ONE_KB_BI . multiply ( FileUtils . ONE_MB_BI ) ; public static final long ONE_TB = ( FileUtils . ONE_KB ) * ( FileUtils . ONE_GB ) ; public static final BigInteger ONE_TB_BI = FileUtils . ONE_KB_BI . multiply ( FileUtils . ONE_GB_BI ) ; public static final long ONE_PB = ( FileUtils . ONE_KB ) * ( FileUtils . ONE_TB ) ; public static final BigInteger ONE_PB_BI = FileUtils . ONE_KB_BI . multiply ( FileUtils . ONE_TB_BI ) ; public static final long ONE_EB = ( FileUtils . ONE_KB ) * ( FileUtils . ONE_PB ) ; public static final BigInteger ONE_EB_BI = FileUtils . ONE_KB_BI . multiply ( FileUtils . ONE_PB_BI ) ; public static final BigInteger ONE_ZB = BigInteger . valueOf ( FileUtils . ONE_KB ) . multiply ( BigInteger . valueOf ( FileUtils . ONE_EB ) ) ; public static final BigInteger ONE_YB = FileUtils . ONE_KB_BI . multiply ( FileUtils . ONE_ZB ) ; public static final File [ ] EMPTY_FILE_ARRAY = new File [ 0 ] ; public static File getFile ( final File directory , final String ... names ) { if ( directory == null ) { <START_BUG> throw new NullPointerException ( "directorydirectory<seq2seq4repair_space>must<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; <END_BUG> } if ( names == null ) { throw new NullPointerException ( "names<seq2seq4repair_space>must<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; } File file = directory ; for ( final String name : names ) { file = new File ( file , name ) ; } return file ; } public static File getFile ( final String ... names ) { } public static String getTempDirectoryPath ( ) { } public static File getTempDirectory ( ) { } public static String getUserDirectoryPath ( ) { } public static File getUserDirectory ( ) { } public static FileInputStream openInputStream ( final File file ) throws IOException { } public static FileOutputStream openOutputStream ( final File file ) throws IOException { } public static FileOutputStream openOutputStream ( final File file , final boolean append ) throws IOException { } public static String byteCountToDisplaySize ( final BigInteger size ) { } public static String byteCountToDisplaySize ( final long size ) { } public static void touch ( final File file ) throws IOException { } public static File [ ] convertFileCollectionToFileArray ( final Collection < File > files ) { } private static void innerListFiles ( final Collection < File > files , final File directory , final IOFileFilter filter , final boolean includeSubDirectories ) { } public static Collection < File > listFiles ( final File directory , final IOFileFilter fileFilter , final IOFileFilter dirFilter ) { } private static void validateListFilesParameters ( final File directory , final IOFileFilter fileFilter ) { } private static IOFileFilter setUpEffectiveFileFilter ( final IOFileFilter fileFilter ) { } private static IOFileFilter setUpEffectiveDirFilter ( final IOFileFilter dirFilter ) { } public static Collection < File > listFilesAndDirs ( final File directory , final IOFileFilter fileFilter , final IOFileFilter dirFilter ) { } public static Iterator < File > iterateFiles ( final File directory , final IOFileFilter fileFilter , final IOFileFilter dirFilter ) { } public static Iterator < File > iterateFilesAndDirs ( final File directory , final IOFileFilter fileFilter , final IOFileFilter dirFilter ) { } private static String [ ] toSuffixes ( final String [ ] extensions ) { } public static Collection < File > listFiles ( final File directory , final String [ ] extensions , final boolean recursive ) { } public static Iterator < File > iterateFiles ( final File directory , final String [ ] extensions , final boolean recursive ) { } public static boolean contentEquals ( final File file1 , final File file2 ) throws IOException { } public static boolean contentEqualsIgnoreEOL ( final File file1 , final File file2 , final String charsetName ) throws IOException { } public static File toFile ( final URL url ) { } @ SuppressWarnings ( "deprecation" ) static String decodeUrl ( final String url ) { } public static File [ ] toFiles ( final URL [ ] urls ) { } public static URL [ ] toURLs ( final File [ ] files ) throws IOException { } public static void copyFileToDirectory ( final File srcFile , final File destDir ) throws IOException { } public static void copyFileToDirectory ( final File srcFile , final File destDir , final boolean preserveFileDate ) throws IOException { } public static void copyFile ( final File srcFile , final File destFile ) throws IOException { } public static void copyFile ( final File srcFile , final File destFile , final boolean preserveFileDate ) throws IOException { } public static long copyFile ( final File input , final OutputStream output ) throws IOException { } private static void doCopyFile ( final File srcFile , final File destFile , final boolean preserveFileDate ) throws IOException { } public static void copyDirectoryToDirectory ( final File srcDir , final File destDir ) throws IOException { } public static void copyDirectory ( final File srcDir , final File destDir ) throws IOException { } public static void copyDirectory ( final File srcDir , final File destDir , final boolean preserveFileDate ) throws IOException { } public static void copyDirectory ( final File srcDir , final File destDir , final FileFilter filter ) throws IOException { }

Fix:
throw new NullPointerException ( "directory<seq2seq4repair_space>must<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ;